This invention is directed to hygienic absorbent articles, such as diapers, training pants and the like. Particularly, the invention is directed to training pants facilitating the toilet training process.
Absorbent articles are well known in the art. These articles typically have an absorbent core held or positioned in proximity to the body of a wearer during use by a fastening system in order to capture and absorb bodily exudates discharged from the wearer. Typical absorbent articles include a topsheet facing the wearer, which permits fluid exudates to pass through, and a backsheet, which prevents the exudates from escaping from the absorbent article.
Disposable absorbent articles such as diapers are designed to absorb and contain bodily waste in order to prevent soiling of the body and clothing of the wearer. The disposable diapers typically comprise a single design available in different sizes to fit a variety of wearers ranging from newborns to toddlers undergoing toilet training. The design of the diaper typically affects performance, such as, ability to absorb and contain bodily waste. The size of the diaper typically affects fit, for example, the size of the diaper waist opening, the size of the openings around the thighs, and the length or xe2x80x9cpitchxe2x80x9d of the diaper.
The toilet training stage may be referred to as the xe2x80x9cpoint of exitxe2x80x9d as toddlers typically leave the product category once training is successfully completed. The age at which children are toilet trained in xe2x80x9cdevelopedxe2x80x9d countries has increased steadily over the past several decades and is now in the range of about 24-42 months. One reason toilet training has become delayed is due to significant technical improvements in diaper dryness and comfort. In modern diapers, the child has dry skin even after one or more urinations. As a result, the child feels little or no discomfort and often may not even be aware that they have urinated.
Many parents have the child wear cotton training pants or underwear during toilet training so the child feels discomfort following urination in their xe2x80x9cpantsxe2x80x9d. It is believed that such discomfort assists with learning or provides motivation to learn proper toilet training. Cotton training pants leave the skin wet and, due to their high breathability, promote evaporative cooling of the skin, further enhancing discomfort. The current tradeoff in this approach, however, is that cotton training pants have poor urine containment leading to wet clothing and often times, wet surroundings e.g. carpeting, furniture, etc. Clearly there is a need to provide a training signal to the toilet training child while preventing urine leakage and unnecessary changes of clothing.
A number of attempts to address this need have been made in the art. One attempt (U.S. Pat. No. 5,681,298) involves the use of a liquid permeable temperature change member to provide a thermal signal to the child. The temperature change member comprises salts having positive (exothermic) or negative (endothermic) heats of solution in water and is disposed with the absorbent assembly. A key requirement is that the total energy change per unit area be about 6 to about 30 cal/cm2. This approach has several critical limitations. First, the liquid permeability of the temperature change member allows the salt to be dissolved and washed into the absorbent assembly, away from the skin of the wearer, significantly reducing the opportunity to provide a thermal signal to the skin. Additionally, the attempt to overcome this phenomenon via the requirement of the 6-30 cal/cm2 total energy change involves the use of significant quantities of the salt, increasing the cost and complexity of the product.
Thus, it would be desirable to provide a wearable article that can facilitate toilet training by providing an effective signal notifying the wearer by causing discomfort when a discharge of bodily waste has occurred while at the same time providing the protection of an absorbent article, preventing soiling of the wearer""s clothing and surroundings. Particularly, it would be desirable to provide such a wearable article providing an effective thermal signal of urination using minimal amounts of endothermic or exothermic salt. Further it would be desirable to provide a thermal signal of urination with less than about 3 cal/cm2 total energy change.
In order to solve one or more of the problems found in the art, a wearable article, such as an absorbent article, is provided with a temperature change element producing a temperature change that is sensed by the skin of the wearer, signaling the wearer that a discharge of bodily exudates, such as urine, has occurred. The temperature change element comprises a permeable layer and an impermeable layer opposite the permeable layer. In certain embodiments, the permeable layer faces the body of the wearer and the impermeable layer faces the absorbent assembly of the wearable article. A temperature change substance, such as an endothermic salt, is interposed between the permeable layer and the impermeable layer.
Once a wearer urinates wetting a target area of the temperature change element aligned with the wearer""s urethra, the permeable layer enables the urine to penetrate through the thickness of the layer in the z-direction. The impermeable layer disposed opposite the permeable layer is not penetrative by the urine in the z direction thereby minimizing the temperature change substance and/or cooled urine from being washed away from the skin of the wearer and into the absorbent assembly or other underlying layers. In addition, the impermeable layer provides a path of least resistance for the movement of fluid between the permeable layer and the impermeable layer in the x-y plane thereby enhancing the amount of temperature change substance wetted therebetween. As a result, urine is able to move into areas of the temperature change element adjacent to the target area thereby increasing the effectiveness of the signal provided by the temperature change element.
Furthermore, since the urine passing through the permeable layer in the z direction does not pass through the impermeable layer into the underlying layers of the article, the temperature change element of the present invention can be made to produce an effective signal utilizing minimal quantities of the temperature change substance. Also, even though temperature change element of the present invention can be made to produce a total unit area energy change ranging from 0.5 cal/cm2 to about 30 cal/cm2, since the permeable layer is held in contact with the wearer""s skin, the wearer feels not only a temperature change effect resulting from an insult of urine but also wetness. Consequently, the temperature change element of the present invention is capable of producing an effective signal at a reduced total unit area energy change ranging from about 0.5 cal/cm2 to about 5.0 cal/cm2.